1. Technical Field
The present invention relates to a device for changing the transport position of products, and particularly of products fed to further processing units. In particular, the present invention relates to a device for aligning sheet material products such as newspaper or magazine signatures moving along a transport path so that the products are not skewed relative to the transport path.
2. Description of the Prior Art
U.S. Pat. No. 4,863,152 discloses a sheet material folding apparatus in which the spacing of sequential products from leading edge to leading edge is being reduced. Products to be transported are conveyed on a first conveyor belt at almost the speed of an upstream printing press. The products are then transferred to a second conveyor belt which moves at a lower conveying speed. The conveyor belts are preferably formed as vacuum belts, in order to lend support to the products to be conveyed; however, the products conveyed thereon are not aligned before they are fed into an angular longitudinal folding device. In order to maintain the products in position on the vacuum belts, suction means must be provided below the conveyor belts which secure the product to be folded also during the performance of the longitudinal fold. As a result, the products may be subjected to very strong mechanical forces which, in the case of very thin product materials, can even result in damage to the products. This type of suction system is costly and has a disadvantageous effect on product quality under certain conditions of production.
Japanese Patent Application No. 2-184717 discloses a mechanism for correcting the skew feeding of paper sheets. The paper sheets which are gripped by several transport rollers are conveyed by a conical roller against a side guide which aligns the sheets. The corrective movement of a paper sheet whose orientation is to be corrected initially takes place from the middle of the paper sheet. This device, too, puts high strain on thin product materials, which can cause damage to the individual products.